The exterior turn signal lights of a vehicle serve many important functions during operation of the vehicle. For examples, activation of the exterior turn signal light informs pedestrian and/or drivers that the driver of the subject vehicle is about to make a turn or wish to make a lane change. In addition, activation of the exterior turn signal light warns other drivers that one is making a lane change. This is particularly important when operating a vehicle in a highway or freeway. Drivers of vehicles occasionally make lane change and turn at intersections, but many of these drivers fail to use the exterior turn signal lights to inform other drivers of the lane change and turn maneuvers. As the result, this increases the risk of having an accident. Each year, approximately 50,000 people die and approximately three million people are injured as the result of traffic accidents. Traffic accidents cost insurance companies and automobile manufacturers over a hundred million dollars each year.
Numerous accident avoidance systems and safety features have been proposed that are intended to prevent or reduce a risk of an accident by warning a driver and/or controlling the vehicle upon recognizing an imminent hazard. For example, U.S. Pat. No. 6,321,159B1 describes a driving lane tracking system that maintains a moving vehicle within a lane. U.S. Pat. No. 6,226,389 B1 describes a motor vehicle warning and control system that uses fuzzy logic to determine a hazardous condition and warns the driver or operates the vehicle when a hazardous condition is detected. Many of these systems are difficult and costly to implement. In addition, the effectiveness of many of these systems depends on the accuracy and reliability of the system in detecting the hazardous condition. An accurate and reliable hazard recognition system is difficult to implement because it is almost impossible to account for all possible road hazards. Hazard recognition systems are also expensive to test. Furthermore, because the dependability of many of the proposed systems that use hazard recognition systems is yet to be determined, drivers of vehicles that use these systems may not feel completely confident or may have difficulty accepting the technologies associated with the systems. Until any of these systems is proven safe and reliable, the preferable accident avoidance system is still the one that relies on drivers' awareness and judgment.
The use of exterior turn signal lights while making lane change has the benefit of improving the awareness of other drivers, and hence, allowing the drivers to make better judgment, such as to brake or to change a direction of motion, in order to avoid an accident. Unfortunately, as mentioned previously, many drivers nowadays are becoming more lazy and reluctant to use the exterior turn signal lights, especially during a lane change situation. As such, inventors of the subject application determine that it is desirable to have an automatic signaling system that can automatically activate the exterior turn signal lights of a vehicle in order to provide warnings to pedestrians and to drivers of other vehicles.
U.S. Pat. No. 5,712,618 describes an automatic signaling device that activates turn signal lights of a vehicle based on a determination of an angle of rotation of a steering wheel, lateral speed and lateral acceleration of the vehicle. U.S. Pat. No. 3,771,096 discloses a lane changing signaling device that employs a rotary electrical connector joined to the steering wheel. None of these systems takes into account that a contour of a lane is constantly changing as one is driving along a roadway. For example, a driver needs to turn a steering wheel in order to steer a vehicle such that it stays within a curved lane. Also, a wheel of a vehicle may be steered towards a right direction (i.e., from a driver's perspective), but yet, the vehicle may be moving towards an adjacent left lane, and vice versa. Because the above described systems activate exterior signal lights based on a rotation of a steering wheel or a turning angle of the wheels of a vehicle, the above described systems would inaccurately activate exterior turn signal lights when the vehicle is making a lane change, and sometimes, even when the vehicle is not making a lane change. Furthermore, different drivers have different driving styles. For example, some drivers tend to sway left and right within a lane more often than other drivers. As such, it would be inaccurate and unreliable to activates exterior turn signal lights based on a rotation of a steering wheel or a turning angle of the wheels of a vehicle.
For the foregoing, inventors of the subject application determine that it would be advantageous to have an automatic turn signal system that can automatically and reliably activate exterior turn signal lights of a vehicle while making lane changes and turns at intersections. Inventors of the subject application also determine that it would be desirable to have an automatic turn signal system that operates independent of a steering direction of a vehicle, and accounts for a changing contour of a lane in which a vehicle is traveling. Furthermore, inventors of the subject application determine that it would be advantageous to have an automatic turn signal system that is adjustable according to the individual driving style of each driver.